Effects of lifelong spontaneous exercise on the M1/M2 macrophage polarization ratio and gene expression in adipose tissue of super-aged mice

Abstract

In the adipose tissue (AT), an increase in the M1 macrophage (M1Ø)/M2 macrophage (M2Ø) polarization ratio can be a risk factor enhancing the inflammatory response during aging, as well as increasing the risk of chronic disease, thereby reducing lifespan, or at least reducing "healthy" lifespan. The purpose of this study was to analyze and compare the AT M1Ø/M2Ø polarization ratio at the final lifespan stage in aged and control animals performing lifelong spontaneous wheel running. Based on flow cytometric analysis, the AT ratio of macrophages revealed M2Ø polarization following lifelong spontaneous exercise (LSE) regardless of age. However, for Icam1 and Tnf, the qPCR analysis showed no difference in gene expressions in young mice; Arg1 expression was higher in Young-EXE (exercising) than in Young-CON (control) mice (p < .0001). In Old-EXE, Icam1 (p < .0001) and Tnf (p < .0001) expression were lower than in Old-CON; for Arg1, gene expression in Old-EXE was higher than in Old-CON (p < .0001). LSE prevents deterioration of physical fitness owing to aging, maintaining high M2Ø polarization levels in the AT. Additionally, LSE does not downregulate Icam1 and Tnf in the AT but appears to suppress the increased M1Ø polarization ratio attributed to aging by upregulating Arg1.

Keywords: Adipose tissue; Aging; Energy homeostasis; Lifelong spontaneous exercise; Macrophage polarization.